package binarySearchTree;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: wx
 * Date: 2024-05-02
 * Time: 12:18
 */
public class BinarySearchTree {
    static class TreeNode {
        public int val;
        public TreeNode left;
        public TreeNode right;
        public TreeNode(int val) {
            this.val = val;
        }
    }
    public TreeNode root;

    /**
     * 最好情况: 完全二叉树 O(logN)
     * 最坏情况: 单分支的树 O(N)
     * @param key
     * @return
     */
    public boolean search(int key) {
        TreeNode cur = root;
        while(cur != null) {
            if (cur.val < key) {
                cur = cur.right;
            }else if (cur.val > key) {
                cur = cur.left;
            }else {
                return true;
            }
        }
        return false;
    }

    public  boolean insert(int val) {
        if (root == null) {
          root = new TreeNode(val);
          return true;
        }
        TreeNode cur = root;
        TreeNode parent = null;
        while(cur != null){
            if (cur.val < val) {
                parent = cur;
                cur = cur.right;
            }else if (cur.val > val) {
                parent = cur;
                cur = cur.left;
            }else {
                return false;
            }
        }
        TreeNode node = new TreeNode(val);
        if (parent.val > val) {
            parent.left = node;
        }else {
            parent.right = node;
        }
        return true;
    }

    public void remove(int key) {
        TreeNode cur = root;
        TreeNode parent = null;
        while(cur != null){
            if (cur.val < key) {
                parent = cur;
                cur = cur.right;
            }else if (cur.val > key) {
                parent = cur;
                cur = cur.left;
            }else {
             //开始删除
                removeNor(cur,parent);
            }
        }
    }

    private void removeNor(TreeNode cur, TreeNode parent) {
        if(cur.left == null){
            if (cur == root) {
                root = cur.right;
            }else if (cur == parent.left) {
                parent.left = cur.right;
            }else {
                parent.right = cur.right;
            }

        }else if (cur.right == null) {
            if (cur == root) {
                root = cur.left;
            }else if (cur == parent.left) {
                parent.left = cur.left;
            }else {
                parent.right = cur.left;
            }

        }else {
            TreeNode targetParent = cur;
            TreeNode target = cur.right;
            while(target.left != null) {
                targetParent = target;
                target = target.left;
            }
            cur.val = target.val;
            //删除target
            if(targetParent.left == target){
                targetParent.left = target.right;
            }else {
                targetParent.right = target.right;
            }

        }
    }
}
